Cutter mandrel

ABSTRACT

There is disclosed a cutter mandrel or arbor for centering and attaching cutting tools to the spindle of machine tools, especially milling machines. The mandrel of the invention comprises a central body member equipped with flange means and a substantially cylindrical portion at the region of said flange means. A substantially conical sleeve member is mounted for lengthwise movement upon the cylindrical portion.

United States Patent Fritz Herrmann Dietikon, Switzerland 790,079

' Jan. 9, 1969 Jan. 12, 197 1 Fritz Bachtold Baltenswil, SwitzerlandJan. 12, 1968 Switzerland No. 475/68 Inventor Appl. No. Filed PatentedAssignee Priority CUTTERMANDREL 4 Claims, 1 Drawing Fig.

US. Cl 90/11,

77/60, 77/71, 279/16, 279/96 Int. Cl B23c 9/00, 82% 31/10 [50] FieldofSearch ..90/1 1.1, 11; 279/1-R, 16, 95, 96, 102, 103; 82/44; 77/71X,60X

[56] References Cited UNITED STATES PATENTS 3,159,081 12/1964 Erikson77/71-X 3,198,079 8/1965 Winnen 90/11-1 Primary Examiner-Gil WeidenfeldAttorney-Werner W. Kleeman ABSTRACT: There is disclosed a cutter mandrelor arbor for I centering and attaching cutting tools to the spindle ofmachine tools, especially milling machines. The mandrel of the inventioncomprises a central body member equipped with flange means and asubstantially cylindrical portion at the region of said flange means. Asubstantially conical sleeve member is mounted for lengthwise movementupon the cylindrical portion.

. CU'I'I'ER MANDREL BACKGROUND OF THE INVENTION Thepresentinventionrelates to an improved cutter 'mandrel or arbor forcentering and securing the cutters or milling tools in the spindles ofmachine tools, especially milling or shaping machines, i a

Cutter mandrels for centering and vatta'ching cutters or milling toolsat the spindles of machine tools constitute a tool which is extensivelyused nowadays. The .builders of machine tools, as well as also themanufacturers, of cutter mandrels have agreed to certain standards, sothat the mandrels can be used at practically all of the machine toolspindles.

The spindlesof machine tools which are designed to receive the cuttermandrels are provided at their end with a conical bore. The latterproduced very exactly and complies with the highest requirementsregarding itstruth in rotation as well as its accuracy in shape. Themandrel possesses the same conical form and is introduced intotheconical bore of the machine spindle. A tensioning screw is introducedfrom the rear through the hollow spindle and serves to retract the coneof the mandrel until it is rigidly mounted in the conical bore of thespiiidle. The forward end of the mandrel. protruding out of the spindlepossesses a flange as well as cylindrical hub, upon which the cutter ormilling tool is mounted. This cutter or milling tool is fixedly pressedagainst the flange of the mandrel by means of a tensioning screw and,thus; is retained in its position.

Since the manufacturers machine tools attempt to produce their spindleswith a very exactly formed conical I bore, 'and since also themanufacturerso'f the mandrels strive to produce the corresponding. conewith extreme accuracy, the introduction of the mandrel 'into the spindleof the machine tools should providea very exact centering and an exactplanar position of the cutter or millingtool. However,

. practice has shown that the positional accuracy of the cutters ormilling tools leave a great deal to be desired. Consequently, during themillingoperation there occurs the well known chattering of the tool, theunclean surfaceand a premature wearing of the tool. Additionally, thefeed movements during machining must be maintained small.

The cause of these occurances is that the conical bore of the machinetool and the cone of the mandrel do not possess the same exact form.Both cones bear upon one another along a rather lengthy path, and thus,even slight deviations in shape are sufl'icient for the axis of theattachment hub for the milling tool to no longer align exactly with thespindle axis, so that the known disadvantageous operating conditionsoccur.

SUMMARY or THE-INVENTION which effectively overcomes the aforementioneddrawbacks of the prior art constructions. I

Another, more specific object of the present invention is to provide animproved cutter mandrel which effectively prevents the occurrence of theaforementioned disadvantageous conditions during the milling operation,and which provides for a very exact centering of the milling tool orcutter and an exact aligned position with respect to the axis of thespindle. i v

Now, in order to implement these and still further objects of theinvention, which will become more readily apparent as the descriptionproceeds, the mandrel designed according to the teachings of theinvention is manifested by the features that is comprises a central bodymember which at the region of its flange possesses a substantiallycylindrical portion upon-which is guided for lengthwise movement asubstantially conical sleeve member.

In the working position of the mandrel, the flange ofthe central bodymember bears against the front end of the spindle of the machine tool.

*BRIEF DESCRIPTION-OF THE DRAWING The invention will be betterunderstood, and objects other than those setforth above, will becomeapparent, when consideration is givenv to the following detaileddescription thereof. Such description makes reference to the annexeddrawing wherein there is shown in schematic sectional view a preferredembodiment of inventive mandrel which is depicted in its work positionat the conical bore of the spindle of a machine tool. 1 v

DESCRIFT ION OF- THE PREFERRED EMBODIMENTS Describing now the drawing,in the single FIG. numeral la designates the forward end of a spindle Iof a machine tool,

this spindle being bored hollow throughout its entire length andpossessing a lengthwise bore 2. It will be seen that at the end of thespindle l'this lengthwise bore 2 communicates with a conical bore 3, thelatter serving to receive the cutter or milling mandrel 7, andtherefore, such is constructed quite exactly. Similarly, the front endface 4 of the spindle I is machined very accurately and issituatedexactly perpendicular to the spindle axis 5. Furthermore, itwill be recognized by referring to the drawing that the conical bore 3of the spindle 1, prior to merging with the lengthwise bore 2 at suchspindle, communicates with a cylindrical bore portion 6'. However, thiscylindrical bore portion 6 is machined less accurately than the conicalbore 3 and the end face 4, and'therefore does not assume any centeringor guiding functions.

Considering now the cutter or milling mandrel 7 in greater detail, itwill be recognized that such embodies a central body member 7a equippedat its front end with a-flange 8, as well as a cylindrical hub 9. Theflange 8 and hub 9 serve for the mounting of the cutter or milling tool10. The milling tool 10 is equipped with a keyway 11 with which engagesa key I2, or

equivalent structure, which is retained at the hub 9, and therefixedlypressed against the surface of the flange 8. The construction of thecomponents 8, 9, I2 and 13 serving for attachment purposes isstandardized and therefore is the same for all mandrels.

Additionally, it willbe seen that the central body member 7a of themandrel 7 possesses at the region of the flange 8 a cylindrical portion14 upon which there is guided for lengthwise movement a conical sleevemember 15. An annular or ring-shaped groove 16 is machined at the cornerbetween the cylindrical portion 14 and the flange 8. An elastic ringmember 17 is inserted in this annular groove 16. This elastic ringmember 17 can be constructed as a metallic spring or as a resilient ringformed of plastic or rubber, by way of example. The conical portion 18of the conical sleeve member 15 possesses exactly the same inclinationas the conical bore 3 provided at the spindle 1. An adjustment orpositioning screw 19 serves as stop and limiting means for the axialmovement of the conical sleeve member 15. Instead of using theadjustment the cylindrical bore portion 6 of thespindle I. This centralbody member 7a possesses a lengthwise bore 21 provided at each of itsends with a respective threading or threaded portion 22 and 23, asshown. A tensioning screw 24, or the like, cooperates with the threading22 and this screw is introduced from the rear through the bore 2 of thespindle 1. This tension-.

ing screw 24 serves to draw the mandrel 7 into its work position, aswill be fully explained hereinafter. The tensioning screw 13 is threadedinto the other threading 23 and serves to fixedly retain the cutter ormilling tool 10.

The mandrel can be brought into its working position in the followingmanner: The central body member 7a of. the mandrel is introducedtogether with the conical'sleeve member 15 into the conical bore 3 ofthe spindle 1. Thereafter, the tensioning screw 24 is introduced andthreaded into the central body member 7a The latter is thereby pulled inaxial direction into the spindle 1 and, specifically, for such length oftime until the flange 8 flushly bears against the end face 4 of thespindle 1.

Since the flange 8 bears snugly against the end face 4 of the spindle l,and therefore, assumes an exactly aligned position to the spindle axis5, the cutter or milling tool 10, which is pressed by the tensioningscrew 13 against the flange 8, also is situated with its axis exactly inthe direction of the axis 5 of the spindle 1.

Centering of the central body member 7a of the mandrel 7, is undertakenthrough the agency of the conical sleeve member 15. During tightening ofthe central body member 711 by the tensioning screw 24, this sleevemember is pressed by means of the elastic ring member 17 into theconical bore 3 of the spindle l. The cylindrical bore 15a of the conicalsleeve member 15 is guided with a narrow fit upon the cylindricalportion 14 of the central body member 7a so that in order to obtain therequired accuracy the relevant cylindrical portions 14 and 15a arelapped together.

The advantage of the inventive mandrel with respect to one having aconical shaft resides in the fact that for maintaining an exact positionthe centering operation is indeed performed by the cone, butadditionally the exact alignedposition is attained due to the bearing ofthe flange 8 against theend face 4 of the spindle l of the machine tool.This is achieved inasmuch as the conical sleeve member 15, which assumesthe function of centering the mandrel, is lengthwise displaceable. Inmandrels with a conical shaft the centering operation and the alignedposition of the bearing surfaces for the cutter or milling tool are onlybrought about by the cone, whereas, the

.flange, which is also necessary for such mandrels, cannot come to bearagainst the end face of the spindle. However, this end face possesses anespecially exact machined surface which would be available formaintaining theexact position of the mandrel.

Naturally, the guiding of the conical sleeve member 15 upon thecylindrical portion 14 is of major importance for the accuracy of themandrel, especially for its centering. Therefore, the accommodation ofthe conical sleeve member 15 upon the central body member 7 and itscylindrical portion 14 must be-achievedwith the greatest accuracy.However. it is considerably simpler to exactly produce two cylindricalparts than two cones of such dimension as occur at mandrels. Moreover,with regard to the manufacturing operations. it is also of advantagethat the conical sleeve member can be maintained relatively small insize, since for the transmission of the forces which occur, the flange 8provides an effective assistance or support.

The cylindrical shaft 20 of the central body member 7 extends, as thusshown in the drawing, up to the cylindrical bore 6. The fit used in thisinstance is relatively large and it is not contemplated to use the bore6 for guiding the mandrel 7.

Since the mandrel 7 renders possible a more exact mounting of the cutteror milling tool 10, the previously experienced chattering no longeroccurs during the milling operation, so that the tool is protected.Additionally, the machined surfaces are therefore cleaner and,furthermore, it is possible to use a greater feed than with theconventional mandrels. Consequently, it is possible to make better useof the capacity of the machine tools.

It should be apparent from the foregoing detailed description, that theobjects set forth at the outset to the specification have beensuccessfully achieved.

lclaim:

1. A mandrel for centering and attaching cutting tools to the spindle ofmachine tools, especially milling machines, comprising a central bodymember equipped with flange means and a substantially cylindricalportion at the region of said flange means, a substantially conicalsleeve member mounted for lengthwise movement upon said cylindricalportion and wherein when said mandrel assumes its working position saidflange means of said central body member bears against a front end faceof the spindle of the machine tool.

2. A mandrel for centering and attaching cutting tools to the spindle ofmachine tools, especially milling machines, comprising a central bodymember equipped with flange means and a substantially cylindricalportion at the region of said flange means, a substantially conicalsleeve member mounted for lengthwise movement upon said cylindricalportion, an annular groove provided at said central body member, anelastic ring member inserted in said annular groove, said conical sleevemember bearing against said elastic ring member.

3. A mandrel as defined in claim 1, further including stop means forlimiting the lengthwise movement of said conical sleeve member.

4. A mandrel as defined in claim 1, wherein said conical sleeve memberis provided with a substantially cylindrical bore for fitting saidconical sleeve member onto said cylindrical portion of said central bodymember, said cylindrical portion of said'central body member and saidcylindrical bore of said conical sleevemember possessing lappedsurfaces.

1. A mandrel for centering and attaching cutting tools to the spindle ofmachine tools, especially milling machines, comprising a central bodymember equipped with flange means and a substantially cylindricalportion at the region of said flange means, a substantially conicalsleeve member mounted for lengthwise movement upon said cylindricalportion and wherein when said mandrel assumes its working position saidflange means of said central body member bears against a front end faceof the spindle of the machine tool.
 2. A mandrel for centering andattaching cutting tools to the spindle of machine tools, especiallymilling machines, comprising a central body member equipped with flangemeans and a substantially cylindrical portion at the region of saidflange means, a substantially conical sleeve member mounted forlengthwise movement upon said cylindrical portion, an annular grooveprovided at said central body member, an elastic ring member inserted insaid annular groove, said conical sleeve member bearing against saidelastic ring member.
 3. A mandrel as defined in claim 1, furtherincluding stop means for limiting the lengthwise movement of saidconical sleeve member.
 4. A mandrel as defined in claim 1, wherein saidconical sleeve member is provided with a substantially cylindrical borefor fitting said conical sleeve member onto said cylindrical portion ofsaid central body member, said cylindrical portion of said central bodymember and said cylindrical bore of said conical sleeve memberpossessing lapped surfaces.